Note 5 - Capital Stock (Details Textual) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended		6 Months Ended
	Jul. 19, 2023	Apr. 27, 2023	Jan. 19, 2023	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Jul. 20, 2022	Jan. 22, 2020
Stock Repurchase Program, Authorized Amount								$ 500,000	$ 500,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 467,000		$ 467,000
Treasury Stock, Shares, Acquired				315,000		498,000
Treasury Stock, Value, Acquired, Cost Method				$ 53,086	$ 164,322	$ 83,935	$ 239,340
Common Stock, Dividends, Per Share, Declared		$ 0.42	$ 0.42
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.42